General

Freebies

SketchUp is not intended for engineering purposes that demand for
high accuracy modeling. However, it is accurate enough to make 3D
models
larger than a few centimeters. For the purposes of architecture
modeling, of course, SketchUp's level of accuracy is sufficient.

Warning

Non Planar Face
SketchUp automatically creates a face when a set of lines make a closed
loop and are all in the same plane.
However, Sketchup also makes a little approximation that even when some
of the lines are a little off (not exactly in one plane), a face will
still be created.
This can be difficult when we try to do push & pull on the face.
The results can be messy or not possible at all. Using inferences will
avoid such problem.

There are three aspects that determine whether models you create are
accurate:

Accuracy in measurements

Accuracy of object positions

Accuracy of object slopes.

SketchUp provides us with various information and techniques in the
form of reference to another object and inference
from existing objects or axis. This will facilitate the making of an
accurate model without always having to specifically enter dimensions
and slopes of objects being created/edited.

Accuracy in measurements

Measurement Box

The surest way to make accurate dimensions and slopes is using Measurement
Box. Almost every object has its own set of parameters depending
on the current tools we choose (context
sensitive). Here are some
examples:

Tip & Trick

Measurement Box
As indicated in "A Fresh Start", Measurement Box is one the three
elements of SketchUp.
Notice that there is no blinking cursor to make input or to edit
value(s) in the input field.
There no other way to enter parameter(s) other than typing blindly
using the keyboard.

Linetool
: [Length]

Rectangletool
: [Wide, Length]

Circletool:
[Sides] [Radius]

Polygontool
: [Sides] [Radius]

Arctool;
[Sides] [Radius] [Bulge]

Freehandtool:
None

Tape Measuretool
: [Length]

Protractortool
: [Angle]

Scaletool
[multiplier], or with the unit symbol, [Desired dimension].

[Bracket] indicates that you have
to press [Enter] after each entry.

Measurement Box is active only during an object
creation,
until we do another mouse operation. As long as we have not done any other mouse operation, we can continue
changing the last entered parameter through the keyboard. The size (or
slope) of
the object will automatically change every time [Enter] key is
pressed.

Scale Tool

Tip & Trick

Scale Tool
Scale tool is used to change the size of existing objects in the model
by dragging one on the available sliding points.
Combining Scale tool with [Ctrl] key will scale object from its
geometry's
center point. Combination of Scale tool with [Shift] key will
scale the object with some uniformity.

Measurement Box can be used only during objects creation. For
existing
objects, change in size can only be made by changing object directly.
One of the methods is by using Scaletool
in Edit toolbar.

When an object is selected using the Scale tool, there will be a
bounding box with several scaling points that can be selected and
dragged by the mouse.
There are 24 scaling points for 3-dimensional objects, and 8 points for
2-dimensional objects. as seen in the figure below. To get an accurate scaling, Scale tool must also be
accompanied by entering parameters through the Measurement box. There
are two ways to use Measurement Box with the scaling tool. First, by
entering a value as the scaling factor, second by inserting a value
complete with dimensional unit(for example: 125cm) in order determine
to final dimension of the aspect being scaled.

Editing using Reference

I am not a fan of Scale tool because sometimes some aspects are not
completely controllable so that the result sometimes would not be as
expected. I prefer using one of the Edit tools and cutting and slicing
the object so that
elements of an object can be individually changed.

Referencing is the next best thing in SketchUp after Push/Pull. By
using references, we can make an object as accurate as possible
(dimension, location, slopes) and use the object as a reference to make
or to edit another object. This saves a lot of time.
Therefore, my work flow to create objects accurately is: Create
initial object(s) and maintain its accuracy using Measurement box, and
reference the object(s) during creating/editing of subsequent
objects.

Reference to Another Object

The most effective and efficient way to edit an object is by
referencing its
change to an existing object. If the referenced object is accurate,
then the edited object will also be accurate.

Push/Pull by
referring to other object

When pushing/pulling a face of an object, we drag it to a new
position to lengthen/ shorten its overall size.
If we move the cursor to a face or any other point in another object to
use it as reference, the face being edited will be at the the same
plane with the referenced face/point. Again, this means that if the
reference is accurate, then the change we are doing to the object will
also be accurate. This is a time saver since we don't need type in any
value whatsoever to make it accurate.

Redoing Last Operation to Another Object

Sketchup has the ability to apply one operation to separate objects
with identical result. This is done by double-clicking other object(s)
after an operation is completed with the initial object . The editing
operation can be
repeated as long as we do not select any other tool.

Redo
Operation
with Double Clicking

With double clicks, the same operation will be applied to all of the
objects.
So if the first editing operation is measured accurately (i.e. using
Measurement Box), all other operation will also be accurate
without having to make any entry with the Measurement Box.

The animation shows how we can repeat an OFFSET operation on several
face shapes. For each double clicking, another shape with the same
contour will be created exactly with the same distance from the
original edges. If we specifically entered a certain length with the
Measurement Box as the offset distance, then all the new shape will
also have the same accurate offset distance. This is how I often do to
make walls in SketchUp.

Adding Guides with a Certain Distance from a Known
Position.

Another method to ensure accuracy is to add guides in the form of
lines or dots to a model to be used as reference in making changes or adding objects. The guide will be
positioned a certain distance from a known line/point in the model
(i.e. one of the Main Axis).
Guides is created using Tape Measuretool or Protractortool.
Tape Measure tool is used to create a parallel guideline at
certain distance from another line, or to create a point at a certain
distance from another point. Protractor tool is used to
create a guideline with a specific angle to a line, (or two points)
that can be used as reference. Guides are usually removed immediately
after their use so as not to obstruct your view.

Creating
"Guides"

The following animation shows examples how to add guides using
the Tape Measure tool and Protractor tool to an object. Note that when
Protractor selected, the cursor changes into an arc /protractor shape.
The usage of this tool should also be followed by entries to the
Measurement Box to ensure accurate position of the guides.

Accuracy of Object Position

The easiest way to ensure accuracy of any object placement is to put
the object in reference to existing object (its midpoint, it's corner,
etc). If the referenced object has been positioned accurately than the
edited object will also accurate to that position. If there is no
object that can be used as a reference, of course, you can always make
Guides to place your object on the location of the guide.

Slope and Angle Accuracy.

We could always set every slope(s)/angle(s) of an object using
Protractortool as previously
discussed. Accurate but not too
practical. If you want to create a line that is parallel or
perpendicular to another line, it is much faster, yet still
accurate, to utilize SketchUp's Automatic Inference.

Tip & Trick

Automatic Inferencing
color
By default, Black line indicates no inferencing is detected. Blue, Red,
Green indicates that inference
is made parallel to one of the main axes. Magenta
and Cyan indicates parallelism,
tangent or perpendicular with a certain existing line.
Note that inferencing behavior is affected by your mouse clicking and
hovering. Some can make a certain inference fail to appear.

Intelligently, SketchUp will always try to inform you whether your
drawing direction has a unique sloping characteristic (parallel,
perpendicular or and tangent, or even equilateral) to one of the main
axes or another nearby line/curve in the model. Therefore, if you
want to make an object which is parallel, perpendicular or tangent to
an existing object, or create equilateral triangle, we don't need to
use Protractor tool at all. With this automatic inference, 3D modeling
can be done easily and quickly, but still be able to maintain accuracy.

Parallel to one of the Main Axes

Most of the time, Main Axes are the main references when
adding/editing an object. Therefore, it is advisable to always use them
as the axes of your model (most of lines are in the model are aligned
with one of these axes). Otherwise, main axes referencing may not as
useful.

Parallel to
one of
the Main Axes

When we want to make a straight line with the Linetool,
Sketchup will automatically indicate whether the line is parallel with
one of the existing axis. Black indicates the line does not align with
any of the axes. The color will change to the color of the axes it is
parallel with. This is very useful, for example, when we want to
make a line perpendicular to the a floor, then we will move the cursor
upward until the resulting line turns blue
and click at desired position.

Referencing to a line not parallel to any of the axes

In addition to the Main Axis inferencing, we can also obtain
inferences from a curve or line that is not parallel to any of
axis

Parallel to another line

Parallel
another line

Creating a line parallel to another line is accomplished by clicking
the starting point of the new line that we want to make and then
hovering your mouse towards the midpoint of the line will be used as a
reference. This will induce inferencing from the line. Next slide the
mouse in the direction approximately parallel to referenced line.
Continue your line when the color turns into Magenta.

Continuing a sloping line.

Continuance of a sloping line

During model creation, we often need to make shape as a continuance
of a sloping objects. For example we want to add eaves to the existing
roof. Instead of creating a new object using Rotate tool, it is
far more quicker to create a line with the same slope with the
roof. I.e. by determining the starting point (end of the sloping
line) and then draw a line using Linetool.
Move your mouse in the
direction that approximately extending the slope and click only when
the line turns Magenta.

Finding other inferences.

Perpendicular to to an edge.

Perpendicular
Line

Making a new line perpendicular to another other line is
accomplished simply by clicking at any point in the referenced
line as a starting point of the new line and and move the cursor to a
direction which is approximately perpendicular to that base line. Click
at the destination point only when the resulting line turns
into Magenta. That
indicates that is has a perpendicular characteristic to the starting
line.

Tangent and Perpendicular with an Equilateral Triangle

Creating a
perfect curve

Automatic Inference will not always provide you with hints regarding
the inference made during an operation. I.e.. when you move your mouse
too fast. However, the inference color will always appear.

The animation shows the following when we use the Arc tool. The
first Magenta inference
indicated that the starting and end point of the curve that will form
an equilateral triangle from a point located between the two sides.
Once we click that position, we will determine the curvature of the arc
we are making. The curve color is Magenta
to indicate that the radius of the circle that forms the curve is
formed are tangent at the start and at end of the curve.